| abstract |
A method of producing a near-infrared absorbing dye compound, useful for image forming materials, infrared heat-sensitive recording devices, optical film materials, and the like, containing a process of reacting a compound represented by formula (I) with peroxomonosulfuric acid or its salt. n n n n n n n n n n n n wherein R 111 , R 112 , R 121 , R 122 , R 131 , R 132 , R 141 and R 142 each independently represent a hydrogen atom, an aliphatic group or an aromatic group; R 103 , R 113 , R 123 , R 133 and R 143 each independently represent a substituent; and n 103 , n 113 , n 123 , n 133 and n 143 each independently denote an integer from 0 to 4. |